This invention relates to a method for detecting photographic image information which can automatically and accurately detect the photographic image information and the size of an original film such as a film negative over the whole area which has been segmented into picture elements, and which can automatically determine the exposure and/or correction amount for photographic printing, and to an apparatus therefor.
In a photographic printer, it is necessary to measure the density of an original film (that is, a film negative or positive) in order to determine exposure or correction amount required for printing the film. In the prior art, the average density of a film negative is photographically measured with respect to its LATD (Large Area Transmittance Density) by a photo-sensor such as a photodiode provided near the light path of an optical system. This image detection of the LATD uniformly determines photometric values of the film negatives, but does not precisely measure the density of images over all of the frame. This leads to such drawbacks as incorrect exposure or uncertain correction.
When an original picture film is exposed on a photographic paper, the exposure and correction amounts should be adjusted depending on the size of the particular film because of the difference in diffusion. In the prior art, the size of the original picture film is judged visually and the size factor is manually inputted via a keyboard or a film negative size status signal is read out from a negative film carrier. But such measures entail complex manipulation of the keyboard or signal processing which sometimes causes errors in input operation.
If the photometric area is to be changed for every film size and the formula of determining exposure is to be selected each time, there are involved further complicated photographic printing processes.